Claude Fable 5.1

claude-fable-5.1

Claude Fable 5 is Anthropic’s Mythos-class model designed for demanding reasoning, software engineering, knowledge work, visual analysis, and scientific research. Built for long-horizon agentic tasks, it can sustain planning and execution across complex workflows, analyze large codebases and documents, and refine its work over multiple steps. Claude Fable 5 is well suited to production applications that require advanced coding, research, professional analysis, and reliable autonomous task completion.

Context Window

1M tokens

Maximum Output

128K tokens

Release Date

Sep 1, 2026

Modalities

Claude Fable 5.1 Pricing

Input PriceOutput PriceCache ReadCache Create 5m
$10/M$50/M$0.25/M$12.5/M

Claude Fable 5.1 API Capabilities

Reasoning

Supported

Tool calling

Supported

Temperature parameter

Not supported

Attachments

Supported

Knowledge Base

2026-06-01

Endpoint Protocols

Messages API

Claude Fable 5.1 Model Highlights

Claude Fable 5.1 combines demanding adaptive reasoning, long-running agentic coding, multimodal document understanding, and a one-million-token context.

Demanding Adaptive Reasoning

Adaptive thinking is always active, with high effort by default for problems that require sustained analysis rather than immediate answers.

Long-Running Agentic Coding

The model can work across entire codebases, write tests, recover from failed steps, and continue autonomous development over extended sessions.

Multimodal Document Context

Text and image inputs, including diagrams, charts, and tables in files or PDFs, can be analyzed within a one-million-token context.

Claude Fable 5.1 Use Cases

Claude Fable 5.1 is suited to ambitious software projects, multi-stage knowledge work, long-running agents, and visual review of technical or business documents.

Ambitious Coding Projects

Implement codebase-wide features, conduct detailed code reviews, optimize performance, and verify results with model-written tests.

Multi-Stage Knowledge Work

Conduct deep research, analyze large collections of material, and convert findings into documents, spreadsheets, or presentations ready for review.

Visual Document Review

Interpret diagrams, charts, and tables embedded in files or PDFs and connect their evidence to legal, financial, analytical, or architectural questions.

How to Use Claude Fable 5.1 via the TokenHub API

curl 'https://us-api.tokenhub.com/v1/messages' \
  -X 'POST' \
  -H "Authorization: Bearer $TOKENHUB_API_KEY"

Claude Fable 5.1 Benchmarks

Index score
Artificial Analysis Intelligence IndexArtificial Analysis broad capability aggregate58.1
Artificial Analysis Coding IndexArtificial Analysis software task aggregate75.2

Metrics sourced from Artificial Analysis

Claude Fable 5.1 Guides & Articles

Claude Fable 5.1 Media and Demos

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Claude Fable 5.1 FAQs

Common questions about Claude Fable 5.1 and using it through TokenHub.

What is Claude Fable 5.1?+

Claude Fable 5.1 is Anthropic’s active flagship model for demanding reasoning and long-horizon agentic work. It accepts text and image input and produces text output.

What is Claude Fable 5.1 best suited for?+

It is designed for long-running agentic coding, multistep research, and complex work with documents, spreadsheets, and slides.

What are its key capabilities and strengths?+

It offers a 1-million-token context window, up to 128K output tokens, vision, tool use, and always-on adaptive thinking controlled through effort settings.

What tradeoffs should I consider?+

Anthropic labels its comparative latency as slower, and its per-token price is higher than Claude Opus 5 or Sonnet 5. Adaptive thinking cannot be disabled, and safety classifiers can return a refusal, so test latency, cost, and refusal handling.

How do I use Claude Fable 5.1 through TokenHub?+

Use the model identifier claude-fable-5-1 in your TokenHub API request, together with the endpoint and credentials shown in your TokenHub account. Test request formatting and response handling before production use.

What are its pricing and availability?+

Anthropic lists Claude Fable 5.1 as active on the Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, and Claude Platform on AWS. Published Claude API rates are $10 per million input tokens, $50 per million output tokens, and $0.25 per million cache-read tokens; TokenHub billing may differ.

When should I choose it over another Claude model?+

Choose it when difficult, long-horizon work needs more capability than your evaluations get from Claude Opus 5 at higher effort. For most routine workloads, Anthropic recommends starting with Claude Opus 5, while faster or cheaper models may be better for high-volume tasks.

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